1. Field of the Invention
The present invention relates generally to the field of industrial printing devices and, more particularly, to an apparatus and method for printing within a predefined print zone on a selected surface of a skewed object while the object is moving in a given direction of travel.
2. Description of the Related Art
In an industrial environment, it is commonly desired to undertake printing within the bounds of a predefined print zone on a selected surface of an object, such as a carton, envelope, vehicle, toy, etc., as it is moved, such as on a conveyor, past a printhead. For optimum printing it is desired that this predefined print zone be in a predetermined alignment or orientation to the direction of travel of the object. Often times, the selected surface of the object is its top. At other times, the selected surface is a side of the object. Difficulty in accomplishing such printing within the bounds of the predefined print zone, regardless of the selected surface, arises when the orientation or position of the object, and thus the orientation of the predefined print zone, is skewed (or out of alignment) with respect to the direction of travel of the object.
For efficiency and speed, such objects moving on a conveyor are printed with images by printheads attached to apparatuses located adjacent to the conveyor. To print the image correctly, the apparatuses must be able to quickly position the printheads in proper relation to the moving objects. If any of the moving objects are skewed, or not aligned properly relative to the direction of travel, this will complicate the printing of the image within the bounds of the predefined print zone on the top or side surfaces of the objects.
Some printing apparatuses force the objects between guide rails in an attempt to deskew the object prior to printing. However, slight variations in object dimensions or objects of different sizes makes these printing apparatuses problematic. Other devices, such as the one shown in U.S. Pat. No. 6,464,314, utilize a spring-biasing system to keep the printhead apparatus in contact with each object that moves past and to keep the printhead close to the object at a fixed predetermined printing distance. However, printing apparatuses that use contact with the passing object to print images thereon present their own set of problems. They tend to be bulky and complex and can damage the passing objects. Moreover, they do not fully address the problem of printing an aligned image on a skewed object.
Thus, there is a need for an innovation which will overcome the aforementioned drawbacks of these prior art industrial printing apparatuses without introducing any significant new drawbacks in place thereof.